Dissolution behavior and early bone apposition of calcium phosphate-coated machined implants

Abstract

Purpose: Calcium phosphate (CaP)-coated implants promote osseointegration and survival rate. The aim of this study was to (1) analyze the dissolution behavior of the residual CaP particles of removed implants and (2) evaluate bone apposition of CaP-coated machined surface implants at the early healing phase.

Methods: Mandibular premolars were extracted from five dogs. After eight weeks, the implants were placed according to drilling protocols: a nonmobile implant (NI) group and rotational implant (RI) group. For CaP dissolution behavior analysis, 8 implants were removed after 0, 1, 2, and 4 weeks. The surface morphology and deposition of the coatings were observed. For bone apposition analysis, block sections were obtained after 1-, 2-, and 4-week healing periods and the specimens were analyzed.

Results: Calcium and phosphorus were detected in the implants that were removed immediately after insertion, and the other implants were composed mainly of titanium. There were no notable differences between the NI and RI groups in terms of the healing process. The bone-to-implant contact and bone density in the RI group showed a remarkable increase after 2 weeks of healing.

Conclusions: It can be speculated that the CaP coating dissolves early in the healing phase and chemically induces early bone formation regardless of the primary stability.

Keywords: Calcium phosphate; Dental implantation; Osseointegration.

Figure 1

Clinical photographs of the experiment. (A) Implant sites were prepared, (B) calcium phosphate-coated machined surface implants were inserted, and (C) after implant placement.

Figure 2

Scanning electron microscopy analysis of implant surfaces (×1,000). (A) Unused implant before insertion, (B) nonmobile implant (NI) that was removed immediately after insertion (0-NI), and (C) nonmobile implant that was removed after a 2-week healing period (2-NI).

Figure 3

Energy dispersive spectrometer analysis of surface of nonmobile implant (NI) group. (A) Implant that was removed immediately after insertion (0-NI), (B) implant that was removed after a 1-week healing period (1-NI), (C) implant that was removed after a 2-week healing period (2-NI), and (D) implant that was removed after a 4-week healing period (4-NI). Ti: titanium, Ca: calcium, P: phosphorus, O: oxygen, Mg: magnesium, C: carbon, Ti: titanium.

Figure 4

Energy dispersive spectrometer analysis of the surface of the rotational implant (RI) group. (A) Implant removed immediately after insertion (0-RI), (B) implant removed after a 1-week healing period (1-RI), (C) implant removed after a 2-week healing period (2-RI), and (D) implant removed after a 4-week healing period (4-RI). Ti: titanium, Ca: calcium, P: phosphorus, O: oxygen, Mg: magnesium, C: carbon, Ti: titanium.

Figure 5

Representative photomicrographs of the nonmobile implant group (H&E, ×50). (A) At 1 week of healing, (B) at 2 weeks of healing, and (C) at 4 weeks of healing. Black arrow: ostectomy line; White arrow: where newly formed woven bone had reached the implant surface; Asterisk: bone particle.

Figure 6

Representative photomicrographs of the rotational implant group (H&E, ×50). (A) At 1 week of healing, (B) at 2 weeks of healing, and (C) at 4 weeks of healing. Black arrow: ostectomy line; White arrow: where newly formed woven bone had reached the implant surface; Asterisk: bone particle.

Figure 7

Representative photomicrographs from two different bone appositional perspectives from a rotational implant specimen at 4 weeks of healing (H&E, ×100). (A) Distant osteogenesis was observed on the coronal part of the implant surface. (B) Contact osteogenesis was observed on the apical part of the implant surface. White arrow: newly formed bone.